The present invention relates to an information memory medium, such as an optical disk, for use in an information processing apparatus, on which information can be recorded and from which it can be reproduced or erased when irradiated by an optical beam, such as a laser beam.
Nowadays, information processing apparatuses which employ an optical disk as a memory medium are in widespread use. During the use of the information processing apparatuses, the information memory medium is held on a turntable. A conventional magnetic memory medium is held on the turntable by a magnetic clamper. The clamper has a magnet, and the turntable is formed of magnetic material. Thus, conventional magnetic memory medium is held on the turntable by the magnetic attraction produced by the clamper. The same type of a magnet clamper is used to hold an optical disk on the turntable of the information processing apparatus.
The inventors hereof have filed U.S. patent application Ser. No. 004,097, which discloses a small-height, lightweight, and low-cost information-processing apparatus having a turntable with a magnet embedded therein, and using an information memory medium (i.e., an optical disk) with a metal plate attached thereto.
This copending application also discloses two types of optical disk. In the first type, the metal plate is directly attached to the main body of the disk. In the second type, the metal plate is connected to a centering member which in turn is attached to the main body of the disk. The information memory medium according to the present invention is of the second type, but is different as regards the means for attaching a metal plate to the centering member of the disk.